Public health has become a broad and flexible concept that encompasses both
the traditional definition of practices that benefit the health of the community
and personal health services, such as hypertension treatment. Legally,
however, the basis for traditional public health and personal health services
are very different. For example, although the state has broad powers to order
vaccination to prevent the spread of a dangerous communicable disease, the
state has limited power to require competent adults to undergo medical
treatment for personal illness such as hypertension.

The core of public health law is coercive action under state authority, the police
power. In the best of circumstances, this authority may be needed only to
encourage educational efforts. At other times, however, public health
authorities must seize property, close businesses, destroy animals, or
involuntarily treat or even lock away individuals. Such powers are rooted in
earlier times, when the fear of pestilential disease was both powerful and well
founded. As communicable diseases such as smallpox, tuberculosis, and polio
were brought under control in the 1960s, the public and even some public
health experts began to believe that there was no longer a need for coercive
public health measures.

The terrorist attack on the United States on September 11, 2001, followed
shortly by anthrax-laden letters sent to public figures, brought bioterrorism to
the public's consciousness, reviving ancient fears of pestilence. The sequella of
Hurricane Katrina and growing fears of pandemic flu have raised questions
about the capabilities of the public health infrastructure and the potential
reach of public health laws in an emergency. These fears have forced a
rethinking of public health law authority.